Merge git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb-2.6
[linux-2.6.git] / fs / posix_acl.c
1 /*
2  * linux/fs/posix_acl.c
3  *
4  *  Copyright (C) 2002 by Andreas Gruenbacher <a.gruenbacher@computer.org>
5  *
6  *  Fixes from William Schumacher incorporated on 15 March 2001.
7  *     (Reported by Charles Bertsch, <CBertsch@microtest.com>).
8  */
9
10 /*
11  *  This file contains generic functions for manipulating
12  *  POSIX 1003.1e draft standard 17 ACLs.
13  */
14
15 #include <linux/kernel.h>
16 #include <linux/slab.h>
17 #include <asm/atomic.h>
18 #include <linux/fs.h>
19 #include <linux/sched.h>
20 #include <linux/posix_acl.h>
21 #include <linux/module.h>
22
23 #include <linux/errno.h>
24
25 EXPORT_SYMBOL(posix_acl_alloc);
26 EXPORT_SYMBOL(posix_acl_clone);
27 EXPORT_SYMBOL(posix_acl_valid);
28 EXPORT_SYMBOL(posix_acl_equiv_mode);
29 EXPORT_SYMBOL(posix_acl_from_mode);
30 EXPORT_SYMBOL(posix_acl_create_masq);
31 EXPORT_SYMBOL(posix_acl_chmod_masq);
32 EXPORT_SYMBOL(posix_acl_permission);
33
34 /*
35  * Allocate a new ACL with the specified number of entries.
36  */
37 struct posix_acl *
38 posix_acl_alloc(int count, gfp_t flags)
39 {
40         const size_t size = sizeof(struct posix_acl) +
41                             count * sizeof(struct posix_acl_entry);
42         struct posix_acl *acl = kmalloc(size, flags);
43         if (acl) {
44                 atomic_set(&acl->a_refcount, 1);
45                 acl->a_count = count;
46         }
47         return acl;
48 }
49
50 /*
51  * Clone an ACL.
52  */
53 struct posix_acl *
54 posix_acl_clone(const struct posix_acl *acl, gfp_t flags)
55 {
56         struct posix_acl *clone = NULL;
57
58         if (acl) {
59                 int size = sizeof(struct posix_acl) + acl->a_count *
60                            sizeof(struct posix_acl_entry);
61                 clone = kmemdup(acl, size, flags);
62                 if (clone)
63                         atomic_set(&clone->a_refcount, 1);
64         }
65         return clone;
66 }
67
68 /*
69  * Check if an acl is valid. Returns 0 if it is, or -E... otherwise.
70  */
71 int
72 posix_acl_valid(const struct posix_acl *acl)
73 {
74         const struct posix_acl_entry *pa, *pe;
75         int state = ACL_USER_OBJ;
76         unsigned int id = 0;  /* keep gcc happy */
77         int needs_mask = 0;
78
79         FOREACH_ACL_ENTRY(pa, acl, pe) {
80                 if (pa->e_perm & ~(ACL_READ|ACL_WRITE|ACL_EXECUTE))
81                         return -EINVAL;
82                 switch (pa->e_tag) {
83                         case ACL_USER_OBJ:
84                                 if (state == ACL_USER_OBJ) {
85                                         id = 0;
86                                         state = ACL_USER;
87                                         break;
88                                 }
89                                 return -EINVAL;
90
91                         case ACL_USER:
92                                 if (state != ACL_USER)
93                                         return -EINVAL;
94                                 if (pa->e_id == ACL_UNDEFINED_ID ||
95                                     pa->e_id < id)
96                                         return -EINVAL;
97                                 id = pa->e_id + 1;
98                                 needs_mask = 1;
99                                 break;
100
101                         case ACL_GROUP_OBJ:
102                                 if (state == ACL_USER) {
103                                         id = 0;
104                                         state = ACL_GROUP;
105                                         break;
106                                 }
107                                 return -EINVAL;
108
109                         case ACL_GROUP:
110                                 if (state != ACL_GROUP)
111                                         return -EINVAL;
112                                 if (pa->e_id == ACL_UNDEFINED_ID ||
113                                     pa->e_id < id)
114                                         return -EINVAL;
115                                 id = pa->e_id + 1;
116                                 needs_mask = 1;
117                                 break;
118
119                         case ACL_MASK:
120                                 if (state != ACL_GROUP)
121                                         return -EINVAL;
122                                 state = ACL_OTHER;
123                                 break;
124
125                         case ACL_OTHER:
126                                 if (state == ACL_OTHER ||
127                                     (state == ACL_GROUP && !needs_mask)) {
128                                         state = 0;
129                                         break;
130                                 }
131                                 return -EINVAL;
132
133                         default:
134                                 return -EINVAL;
135                 }
136         }
137         if (state == 0)
138                 return 0;
139         return -EINVAL;
140 }
141
142 /*
143  * Returns 0 if the acl can be exactly represented in the traditional
144  * file mode permission bits, or else 1. Returns -E... on error.
145  */
146 int
147 posix_acl_equiv_mode(const struct posix_acl *acl, mode_t *mode_p)
148 {
149         const struct posix_acl_entry *pa, *pe;
150         mode_t mode = 0;
151         int not_equiv = 0;
152
153         FOREACH_ACL_ENTRY(pa, acl, pe) {
154                 switch (pa->e_tag) {
155                         case ACL_USER_OBJ:
156                                 mode |= (pa->e_perm & S_IRWXO) << 6;
157                                 break;
158                         case ACL_GROUP_OBJ:
159                                 mode |= (pa->e_perm & S_IRWXO) << 3;
160                                 break;
161                         case ACL_OTHER:
162                                 mode |= pa->e_perm & S_IRWXO;
163                                 break;
164                         case ACL_MASK:
165                                 mode = (mode & ~S_IRWXG) |
166                                        ((pa->e_perm & S_IRWXO) << 3);
167                                 not_equiv = 1;
168                                 break;
169                         case ACL_USER:
170                         case ACL_GROUP:
171                                 not_equiv = 1;
172                                 break;
173                         default:
174                                 return -EINVAL;
175                 }
176         }
177         if (mode_p)
178                 *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
179         return not_equiv;
180 }
181
182 /*
183  * Create an ACL representing the file mode permission bits of an inode.
184  */
185 struct posix_acl *
186 posix_acl_from_mode(mode_t mode, gfp_t flags)
187 {
188         struct posix_acl *acl = posix_acl_alloc(3, flags);
189         if (!acl)
190                 return ERR_PTR(-ENOMEM);
191
192         acl->a_entries[0].e_tag  = ACL_USER_OBJ;
193         acl->a_entries[0].e_id   = ACL_UNDEFINED_ID;
194         acl->a_entries[0].e_perm = (mode & S_IRWXU) >> 6;
195
196         acl->a_entries[1].e_tag  = ACL_GROUP_OBJ;
197         acl->a_entries[1].e_id   = ACL_UNDEFINED_ID;
198         acl->a_entries[1].e_perm = (mode & S_IRWXG) >> 3;
199
200         acl->a_entries[2].e_tag  = ACL_OTHER;
201         acl->a_entries[2].e_id   = ACL_UNDEFINED_ID;
202         acl->a_entries[2].e_perm = (mode & S_IRWXO);
203         return acl;
204 }
205
206 /*
207  * Return 0 if current is granted want access to the inode
208  * by the acl. Returns -E... otherwise.
209  */
210 int
211 posix_acl_permission(struct inode *inode, const struct posix_acl *acl, int want)
212 {
213         const struct posix_acl_entry *pa, *pe, *mask_obj;
214         int found = 0;
215
216         FOREACH_ACL_ENTRY(pa, acl, pe) {
217                 switch(pa->e_tag) {
218                         case ACL_USER_OBJ:
219                                 /* (May have been checked already) */
220                                 if (inode->i_uid == current_fsuid())
221                                         goto check_perm;
222                                 break;
223                         case ACL_USER:
224                                 if (pa->e_id == current_fsuid())
225                                         goto mask;
226                                 break;
227                         case ACL_GROUP_OBJ:
228                                 if (in_group_p(inode->i_gid)) {
229                                         found = 1;
230                                         if ((pa->e_perm & want) == want)
231                                                 goto mask;
232                                 }
233                                 break;
234                         case ACL_GROUP:
235                                 if (in_group_p(pa->e_id)) {
236                                         found = 1;
237                                         if ((pa->e_perm & want) == want)
238                                                 goto mask;
239                                 }
240                                 break;
241                         case ACL_MASK:
242                                 break;
243                         case ACL_OTHER:
244                                 if (found)
245                                         return -EACCES;
246                                 else
247                                         goto check_perm;
248                         default:
249                                 return -EIO;
250                 }
251         }
252         return -EIO;
253
254 mask:
255         for (mask_obj = pa+1; mask_obj != pe; mask_obj++) {
256                 if (mask_obj->e_tag == ACL_MASK) {
257                         if ((pa->e_perm & mask_obj->e_perm & want) == want)
258                                 return 0;
259                         return -EACCES;
260                 }
261         }
262
263 check_perm:
264         if ((pa->e_perm & want) == want)
265                 return 0;
266         return -EACCES;
267 }
268
269 /*
270  * Modify acl when creating a new inode. The caller must ensure the acl is
271  * only referenced once.
272  *
273  * mode_p initially must contain the mode parameter to the open() / creat()
274  * system calls. All permissions that are not granted by the acl are removed.
275  * The permissions in the acl are changed to reflect the mode_p parameter.
276  */
277 int
278 posix_acl_create_masq(struct posix_acl *acl, mode_t *mode_p)
279 {
280         struct posix_acl_entry *pa, *pe;
281         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
282         mode_t mode = *mode_p;
283         int not_equiv = 0;
284
285         /* assert(atomic_read(acl->a_refcount) == 1); */
286
287         FOREACH_ACL_ENTRY(pa, acl, pe) {
288                 switch(pa->e_tag) {
289                         case ACL_USER_OBJ:
290                                 pa->e_perm &= (mode >> 6) | ~S_IRWXO;
291                                 mode &= (pa->e_perm << 6) | ~S_IRWXU;
292                                 break;
293
294                         case ACL_USER:
295                         case ACL_GROUP:
296                                 not_equiv = 1;
297                                 break;
298
299                         case ACL_GROUP_OBJ:
300                                 group_obj = pa;
301                                 break;
302
303                         case ACL_OTHER:
304                                 pa->e_perm &= mode | ~S_IRWXO;
305                                 mode &= pa->e_perm | ~S_IRWXO;
306                                 break;
307
308                         case ACL_MASK:
309                                 mask_obj = pa;
310                                 not_equiv = 1;
311                                 break;
312
313                         default:
314                                 return -EIO;
315                 }
316         }
317
318         if (mask_obj) {
319                 mask_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
320                 mode &= (mask_obj->e_perm << 3) | ~S_IRWXG;
321         } else {
322                 if (!group_obj)
323                         return -EIO;
324                 group_obj->e_perm &= (mode >> 3) | ~S_IRWXO;
325                 mode &= (group_obj->e_perm << 3) | ~S_IRWXG;
326         }
327
328         *mode_p = (*mode_p & ~S_IRWXUGO) | mode;
329         return not_equiv;
330 }
331
332 /*
333  * Modify the ACL for the chmod syscall.
334  */
335 int
336 posix_acl_chmod_masq(struct posix_acl *acl, mode_t mode)
337 {
338         struct posix_acl_entry *group_obj = NULL, *mask_obj = NULL;
339         struct posix_acl_entry *pa, *pe;
340
341         /* assert(atomic_read(acl->a_refcount) == 1); */
342
343         FOREACH_ACL_ENTRY(pa, acl, pe) {
344                 switch(pa->e_tag) {
345                         case ACL_USER_OBJ:
346                                 pa->e_perm = (mode & S_IRWXU) >> 6;
347                                 break;
348
349                         case ACL_USER:
350                         case ACL_GROUP:
351                                 break;
352
353                         case ACL_GROUP_OBJ:
354                                 group_obj = pa;
355                                 break;
356
357                         case ACL_MASK:
358                                 mask_obj = pa;
359                                 break;
360
361                         case ACL_OTHER:
362                                 pa->e_perm = (mode & S_IRWXO);
363                                 break;
364
365                         default:
366                                 return -EIO;
367                 }
368         }
369
370         if (mask_obj) {
371                 mask_obj->e_perm = (mode & S_IRWXG) >> 3;
372         } else {
373                 if (!group_obj)
374                         return -EIO;
375                 group_obj->e_perm = (mode & S_IRWXG) >> 3;
376         }
377
378         return 0;
379 }